The Kerala Government is planning to amend the Kerala Panchayat Raj and Kerala Municipality Acts to implement the proposal in the latest budget to impose a special property tax on people owning more than one house and collect tax from owners of vacant buildings.
Current rules allow total waiver of property tax (vacancy remission) on vacant houses. When the amendment comes into force, this remission would no longer be available and tax needs to be paid. The property tax on vacant houses would be decided based on the area and age of the buildings.

Local bodies in Kerala collect property tax on a half-yearly basis during the periods April 1 to September 30 and October 1 to March 31. Owners of vacant houses can submit applications to the respective local bodies and vacancy remission is granted based on the report submitted by the revenue inspectors after a site inspection.
As per the latest data with the Local Self-Government (LSG) Department, there are 18 lakh vacant houses across Kerala. The LSG Department is presently exploring IT-based options along with the Information Kerala Mission to identify the new houses and those owned by people having other properties, among these vacant buildings.

Courtesy : 

https://www.onmanorama.com/news/kerala/2023/02/05/local-body-laws-amended-with-special-tax-second-vacant-houses.html